Tubulointerstitial nephritis (TIN) is characterized by abnormalities of renal tubules and interstitium with infiltration of mononuclear and polymorphonuclear leukocytes. Immunologically mediated forms of TIN have been investigated in animal models induced by immunization with kidney tubular basement membrane (TBM) and crude kidney tissue. Cellular and humoral immune responses are variably involved in the pathogenesis of TIN in these models. While immunopathological mechanisms have been investigated extensively in model systems, little is understood about the identity and roles of kidney components in the disease process. In man, TIN is associated with anti-TBM antibodies and cellular immune elements are thought to play a predominant role. This research program will further characterize a component of TBM (TIN antigen (TA)) that reacts with anti-TBM sera in human TIN and induces TIN in rats. Structural relationships between molecular weight forms of TA will be investigated. Ultrastructural localization of TA will be characterized. Cell binding of TA and its interaction with other matrix components will be studied. Protein sequence of TA will be deduced by sequencing cDNA. Methods include: protein isolation by column chromatography, characterization by electrophoresis, chemical analysis, protein sequencing and immunochemical assays. Monoclonal antibodies will be developed and molecular biology techniques, including screening of a cDNA library, PCR, DNA sequencing and Northern analysis will be employed. Electron microscopy will be used for ultrastructural characterization of antibody binding and to define molecular properties of TA and its interactions with other molecules. The applicant's long-term objectives are to elucidate roles of extracellular matrix components in renal disease, to characterize structure and functions of renal basement membrane components, and to define composition and organization of basement membranes in the kidney.